**2.1. Aristotle**

Aristotle1 was the son of Nicomachus, the personal physician of King Amyntas of Macedon and Phaestis, a wealthy woman2. Nicomachus may have been involved in dissections (Ellwood 1938, p. 36), a key tool in Aristotle's biological studies, particularly on marine mammals. Aristotle lost both his parents when he was about 10 and from then on he was raised of his uncle and/or guardian Proxenus, also a physician (Moseley 2010, p. 6). Early Greek physicians known as asclepiads usually taught their children reading, writing, and anatomy (Moseley 2010, p. 10).

When Whales Became Mammals:

The Scientific Journey of Cetaceans From Fish to Mammals in the History of Science 5

dissected but others were based on tales and he warned about the accuracy of those descriptions. For example, although he mentioned information in numerous occasions provided to him by fishers, many times (but not always) he debunks some of the fallacies he

Of what we would consider today as mammals (including cetaceans) he described about 80 and about 130 species of fishes, which, again, underlines the extensive work, he did on marine creatures, mostly while living at Lesbos. Under the genus "Cetacea" he included at least three species: (1) "dolphins" probably a combination of striped dolphin (*Stenella coeruleoalba*, the most frequent species in the Mediterranean), the common dolphin (*Delphinus delphis*), and the bottlenose dolphin (*Tursiops truncatus*); (2) the harbor porpoise (*Phocoena phocoena*) which he described as "similar to dolphins but smaller and found in the Black Sea" ("Euxine") (*HA* 566b9)4; and, (3) the fin whales (*Balaenoptera physalus*) another

The motives behind Aristotle classification system, particularly animals, were not biological in nature but rather philosophical. For him these creatures were evidence for rational order in the universe. This approach meant that species were rigid elements of the world and, thus, he never contemplated mutability or anything close to evolution, despite the fact that earlier Greek philosophers such as Anaximander envisioned the mutability of species. Furthermore, Aristotle's motive for conducting this categorization was done in such a way that we can then identify the causes that explain why animals are organized the way they are. His investigation into those causes is carried out in other surviving biological works (e.g., *Parts of Animals*). When describing species he adhered to his teleological doctrine of

Aristotle was able to distinguish between homology and analogy, recognizing cetaceans as a natural group with many similarities with other mammals ("viviparous quadrupeds"). He considered cetaceans as "blooded" animals, adding, "viviparous such as man, and the horse, and all those animals that have hair; and of the aquatic animals, the whale kind as the dolphin and cartilaginous fishes" (*HA* 489a34-489b3). He also wrote: "all creatures that have a blow-hole respire and inspire, for they are provided with lungs. The dolphin has been seen asleep with its nose above water as he snores (*HA* 566b14). All animals have breasts that are internally or externally viviparous, as for instance all animals that have hair, as man and the horse; and the cetaceans, as the dolphin, porpoise and the whale -for these animals have breasts and are supplied with milk" (*HA* 521b21-25). Among the species he described were dolphins, orcas, and baleen whales, noting that "the [whale] has no teeth but does have hair that resemble hog bristle" (*HA* 519b9-15). Thus, he was the first to separate whales and

However, Aristotle placed whales and dolphins below reptiles and amphibians, because their lack of legs, despite his physiological and behavioral observations that they were

related more closely to "viviparous quadrupeds" than to fish.

4 These citations for *Historia Animalium* follow the Bekker' pagination.

heard based on his own observations, particularly when it came to reproduction.

common species in the Mediterranean at that time.

purposiveness in nature.

dolphins from fish.

In 367 BCE Aristotle moved to Athens to study at Plato's Academy, and later travelled throughout Asia Minor and studied living organisms while at the island of Lesbos (344-342 BCE) where he collected a lot of information about marine mammals. He later created his own philosophical school, the Lyceum, in Athens where most of his written work was produced between 335 and 323 BCE.

Aristotle is the first natural historian from whom we have any extensive work. One of his surviving opuses is *Historia Animalium* (inquiry about animals)3. There he classified animals as follows (beginning from the top): "blooded" animals (referring to those with red blood, vertebrates) with humans at the top, viviparous quadrupeds (what we would call terrestrial mammals), oviparous quadrupeds (legged reptiles and amphibians), birds, cetaceans, fishes, and then "bloodless" animals (invertebrates). He named each one of these groups a "genus."

Humans Viviparous quadrupeds (terrestrial mammals) Oviparous quadrupeds (reptiles and amphibians) Birds Cetaceans Fish Malacia (squids and octopuses) Malacostraca (crustaceans) Ostracoderma (bivalve mollusks) Entoma (insects, spiders, etc.) Zoophyta (jellyfishes, sponges, etc.) Higher plants Lower plants

Based on the "kinds" of animals and the varieties he described we can distinguish somewhere between 550 and 600 species. Most of them he had observed directly and even

<sup>1</sup> *b*. Stagira, Chalcidice, Macedonia, today's Greece, 384 BCE; *d*. Chalcis, Euboea, Ancient Greece, today's Greece 322 BCE

<sup>2</sup> Biographical information on Aristotle is largely based on Barnes (1995).

<sup>3</sup> We used the text available at http://classics.mit.edu/Aristotle/history\_anim.html

dissected but others were based on tales and he warned about the accuracy of those descriptions. For example, although he mentioned information in numerous occasions provided to him by fishers, many times (but not always) he debunks some of the fallacies he heard based on his own observations, particularly when it came to reproduction.

4 New Approaches to the Study of Marine Mammals

Aristotle1 was the son of Nicomachus, the personal physician of King Amyntas of Macedon and Phaestis, a wealthy woman2. Nicomachus may have been involved in dissections (Ellwood 1938, p. 36), a key tool in Aristotle's biological studies, particularly on marine mammals. Aristotle lost both his parents when he was about 10 and from then on he was raised of his uncle and/or guardian Proxenus, also a physician (Moseley 2010, p. 6). Early Greek physicians known as asclepiads usually taught their children reading, writing, and

In 367 BCE Aristotle moved to Athens to study at Plato's Academy, and later travelled throughout Asia Minor and studied living organisms while at the island of Lesbos (344-342 BCE) where he collected a lot of information about marine mammals. He later created his own philosophical school, the Lyceum, in Athens where most of his written work was

Aristotle is the first natural historian from whom we have any extensive work. One of his surviving opuses is *Historia Animalium* (inquiry about animals)3. There he classified animals as follows (beginning from the top): "blooded" animals (referring to those with red blood, vertebrates) with humans at the top, viviparous quadrupeds (what we would call terrestrial mammals), oviparous quadrupeds (legged reptiles and amphibians), birds, cetaceans, fishes, and then "bloodless" animals (invertebrates). He named each one of these groups a "genus."

Based on the "kinds" of animals and the varieties he described we can distinguish somewhere between 550 and 600 species. Most of them he had observed directly and even

<sup>1</sup> *b*. Stagira, Chalcidice, Macedonia, today's Greece, 384 BCE; *d*. Chalcis, Euboea, Ancient Greece, today's

2 Biographical information on Aristotle is largely based on Barnes (1995). 3 We used the text available at http://classics.mit.edu/Aristotle/history\_anim.html

**2. Ancient times** 

anatomy (Moseley 2010, p. 10).

produced between 335 and 323 BCE.

Viviparous quadrupeds (terrestrial mammals) Oviparous quadrupeds (reptiles and amphibians)

Malacia (squids and octopuses) Malacostraca (crustaceans) Ostracoderma (bivalve mollusks) Entoma (insects, spiders, etc.) Zoophyta (jellyfishes, sponges, etc.)

Humans

Birds Cetaceans Fish

Higher plants Lower plants

Greece 322 BCE

**2.1. Aristotle** 

Of what we would consider today as mammals (including cetaceans) he described about 80 and about 130 species of fishes, which, again, underlines the extensive work, he did on marine creatures, mostly while living at Lesbos. Under the genus "Cetacea" he included at least three species: (1) "dolphins" probably a combination of striped dolphin (*Stenella coeruleoalba*, the most frequent species in the Mediterranean), the common dolphin (*Delphinus delphis*), and the bottlenose dolphin (*Tursiops truncatus*); (2) the harbor porpoise (*Phocoena phocoena*) which he described as "similar to dolphins but smaller and found in the Black Sea" ("Euxine") (*HA* 566b9)4; and, (3) the fin whales (*Balaenoptera physalus*) another common species in the Mediterranean at that time.

The motives behind Aristotle classification system, particularly animals, were not biological in nature but rather philosophical. For him these creatures were evidence for rational order in the universe. This approach meant that species were rigid elements of the world and, thus, he never contemplated mutability or anything close to evolution, despite the fact that earlier Greek philosophers such as Anaximander envisioned the mutability of species. Furthermore, Aristotle's motive for conducting this categorization was done in such a way that we can then identify the causes that explain why animals are organized the way they are. His investigation into those causes is carried out in other surviving biological works (e.g., *Parts of Animals*). When describing species he adhered to his teleological doctrine of purposiveness in nature.

Aristotle was able to distinguish between homology and analogy, recognizing cetaceans as a natural group with many similarities with other mammals ("viviparous quadrupeds"). He considered cetaceans as "blooded" animals, adding, "viviparous such as man, and the horse, and all those animals that have hair; and of the aquatic animals, the whale kind as the dolphin and cartilaginous fishes" (*HA* 489a34-489b3). He also wrote: "all creatures that have a blow-hole respire and inspire, for they are provided with lungs. The dolphin has been seen asleep with its nose above water as he snores (*HA* 566b14). All animals have breasts that are internally or externally viviparous, as for instance all animals that have hair, as man and the horse; and the cetaceans, as the dolphin, porpoise and the whale -for these animals have breasts and are supplied with milk" (*HA* 521b21-25). Among the species he described were dolphins, orcas, and baleen whales, noting that "the [whale] has no teeth but does have hair that resemble hog bristle" (*HA* 519b9-15). Thus, he was the first to separate whales and dolphins from fish.

However, Aristotle placed whales and dolphins below reptiles and amphibians, because their lack of legs, despite his physiological and behavioral observations that they were related more closely to "viviparous quadrupeds" than to fish.

<sup>4</sup> These citations for *Historia Animalium* follow the Bekker' pagination.

Aristotle followed his teacher Plato in classifying animals by progressively dividing them based on shared characters. This is an embryonic form of today's classification more fully developed by Linnaeus. The reason he ordered the different "genera" the way he did was because he considered "vital heat" (characterized by method of reproduction, respiration, state at birth, etc.) as an index of superiority placing humans at the very top. Men were superior to women because they had more "vital heat." On this he followed Hippocrates's ideas, since the Greek physician thought there was an association between temperature and soul.

When Whales Became Mammals:

The Scientific Journey of Cetaceans From Fish to Mammals in the History of Science 7

Aristotle's influence on naturalists' classification of life would extend until Darwin's times

Pliny the Elder6 was the son of an equestrian (the lower of the two aristocratic classes in Rome) and was educated in Rome. After serving in the military he became a lawyer and then a government bureaucrat. In these positions he travelled not only throughout what is Italy today but also what it would later became Germany, France and Spain as well as North

He wrote a 37-volume *Naturalis Historia7* (ca. 77-79) in which according to himself he had compiled "20,000 important facts, extracted from about 2000 volumes by 100 authors" and was written for "the common people, the mass of peasants and artisans, and only then for those who devote themselves to their studies at leisure" (Preface 6). This is the earliest known encyclopedia of any kind, which has been interpreted as a Roman invention in order to compile information about the empire (Naas 2002, Murphy 2004). It was a rather disorganized book, whose prose has been criticized by many (Locher 1984). Pliny seemed to be more interested in what appeared to be curiousities than what were facts. This is a big

He devoted 9 of the 37 volumes to animals and ordered them according to where they live. Volume IX (*Historia Aquatilium*) of *Naturalis Historia* is devoted to aquatic creatures, whether living in oceans, rivers or lakes, whether vertebrate or invertebrate, real or mythical. Based on their size he categorized as "monster" anything big, whether it is a whale, a sawfish or a

He grouped together all known species of cetaceans (*cete*) but constantly mixed their descriptions with those of other marine mammals such as seals as well as with cartilaginous fishes, such as some sharks (*pristis*). Pliny mentioned the three species cited by Aristotle: dolphins (*delphinus*, probably a combination of striped dolphin [*Stenella coeruleoalba*] and the common dolphin [*Delphinus delphis*], IX 12-34), porpoises (*porcus marinus*, the harbor porpoise [*Phocoena phocoena*], IX 45) and whales (*ballaena*, possibly a combination of large toothless whales [mysticetes] IX 12-13). Then he added a few more: the *thursio* or *tirsio* (probably the bottlenose dolphin, *Tursiops truncatus* IX 34), the *physeter* (probably the sperm whale [*Physeter macrocephalus*] IX 8) found in the "Gallic Ocean" (probably the Bay of Biscay, IX 3, 4), the *orca* (probably the killer whale [*Orcinus orca*] IX 12-14), and the river dolphin from India (possibly *Platanista gangetica*, IX 46). He also mentioned some mythical creatures such as *Homo marinus* (Sea-Man, IX 10) and the *Scolopendra marina* (IX, 145) a mythical

<sup>6</sup> *b*. as Gaius Plinius Secundus 23/24 CE in what is now Como, Italy; *d*. 25 August 79 CE near Pompeii,

http://www.perseus.tufts.edu/hopper/text?doc=Plin.+Nat.+toc&redirect=true

when evolutionary views replaced the fixity of species as elements in nature.

collection of facts and fictions, based mostly said on things said by others.

**2.2. Pliny the elder** 

Africa (Reynolds 1986).

tuna (IX 2,3).

Italy.

7 I used the version available at:

Yet he was not fully satisfied by this approach given that a number of "genera" had characters that were shared across groups, particularly when compared with their habitats. For example, both fishes and cetaceans had fins, but they differ markedly on other characters such as reproduction (oviparous vs. viviparous) or organs (gills vs. lungs, respectively).

Many of Aristotle's observations about cetaceans remain accurate. In terms of internal anatomy he mentioned that they have internal reproductive organs (*HA* 500a33-500b6), that dolphins, porpoises, and whales copulate and are viviparous, giving birth to between one and two offsprings having two breasts located near the genital openings that produce milk (*HA* 504b21), that dolphins reach full size at the age of 10 and their period of gestation is 10 months, show parental care, some may live up to 30 years and this is known because fishers can individually identify them by marks on their bodies (*HA* 566b24), and that dolphins have bones (*HA* 516b11).

Regarding behavior and sensory organs he said that dolphins have a sense of smell but he could not find the organ (*HA* 533b1), that dolphins can hear despite the lack of ears (*HA* 533b10-14), produce sounds when outside the water (*HA* 536a1), that dolphins and whales sleep with their blowhole above the surface of the water (*HA* 537a34), are carnivorous (*HA* 591b9-15), and swim fast (*HA* 591b29).

He held that cetaceans are not fishes because they have hair, lungs (*HA* 489a34), lack gills, suckle their young by means of mammae, they are viviparous (*HA* 489b4), and that their bones are analogous to the mammals, not fishes. Still they he calls them "fishes" (*HA* 566b2-5).

These basic Aristotelian biological descriptions persisted for good and for bad until Charles Darwin's evolutionary work. On one hand his descriptions were so accurate that Darwin admired Aristotle, to the point that he said privately that the intellectual heroes of his own time "were mere schoolboys compared to old Aristotle."5 Yet the fact that Aristotle saw the natural world as fixed in time with no room for evolution and that he kept calling cetaceans "fishes," would delay intellectual progress for many centuries when it came to the classification of these animals.

<sup>5</sup> Darwin Correspondence Database, http://www.darwinproject.ac.uk/entry-11875 accessed on 25 Feb 2012.

Aristotle's influence on naturalists' classification of life would extend until Darwin's times when evolutionary views replaced the fixity of species as elements in nature.
